Ostomy appliances equipped with "two-piece couplings," as they are now commonly described, have been known for many years. For example, U.S. Pat. No. 3,528,420 discloses such an appliance having two deformable plastic rings, one of the rings 20 being secured to a faceplate 16 and the other ring 14 being attached to an ostomy pouch 10. A flange 26 on the inner ring is intended to provide an abutment for the outer ring to latch and seal the rings together until separation is desired.
Other types of two-piece couplings are known, as disclosed in U.S. Pat. Nos. 4,419,100, 4,170,231, 4,359,051, 3,948,256, and British Pat. No. 1,571,657. In all such constructions, latching and sealing functions are performed by the coupling rings themselves without the involvement or intervention of other elements or components. However, such sealing and latching functions may occur at different locations along the rings, as disclosed in co-pending co-owned application No. 611,423, filed May 17, 1984. In that application, one of the rings has an axially-extending frusto-conical neck portion and the other ring has a frusto-conical collar portion detachably receiving and sealingly engaging the neck portion. Primary latching is achieved in an annular zone spaced a substantial distance radially outwardly from the area of sealing engagement between the neck and collar portions, such latching action being provided by a shoulder extending about the outer periphery of one of the rings and a latching ring, defining a shoulder-receiving recess, extending about the outer periphery of the other ring.